(1) Field of the Invention
The present invention relates to cleaning nozzles and substrate cleaning apparatus for performing cleaning treatment of semiconductor substrates, glass substrates for liquid crystal displays, glass substrates for photomasks, substrates for optical disks and the like (hereinafter referred to simply as substrates) by supplying a cleaning solution to the substrates, and film removing treatment of such substrates by supplying a treating solution to the substrates to remove film coatings therefrom. More particularly, the invention relates to cleaning treatment and film removing treatment performed by supplying substrates with a cleaning solution converted to mist by mixing a pressurized gas therewith.
(2) Description of the Related Art
A conventional cleaning of substrates, i.e. scrub cleaning, includes physical cleaning for removing particles and the like from surfaces of substrates without using a chemical solution, and chemical cleaning for removing particles and the like from surfaces of substrates by using a chemical solution or gas.
Typical examples of physical cleaning include a xe2x80x9cbrush scrub methodxe2x80x9d in which a brush is placed in direct contact with a substrate surface spinning at high speed to scrub the substrate surface, and an xe2x80x9cultrasonic scrub methodxe2x80x9d in which super pure water with ultrasonic wave applied thereto is supplied to a substrate surface to apply ultrasonic vibration thereto. Typical examples of chemical cleaning include an xe2x80x9cice scrub methodxe2x80x9d which delivers minute ice particles toward a substrate (see T. Ohmori et al.: Ultra Clean Technology 1, 35 (1990)), a xe2x80x9cdry ice scrub methodxe2x80x9d which provides cleaning with dry ice (see S. A. Hoening: SEMI Tech. Symp. Proc., Tokyo, p.G-I-I (1985)), a xe2x80x9csolid argon scrub methodxe2x80x9d which provides cleaning with argon gas (see W. McDormotto et al.: Microcontamination 9, 33 (1991)), and a xe2x80x9cmist jet scrub methodxe2x80x9d for delivering a cleaning solution converted to mist by mixing a pressurized gas therewith, from a pressure type binary fluid cleaning nozzle toward a substrate. Further, a xe2x80x9ccompound methodxe2x80x9d is known which combines a physical cleaning method and a chemical cleaning method.
In manufacturing integrated circuits (LSI or large scale integrated circuits) on semiconductor substrates, for example, increasingly minute patterns are fabricated into the substrates with progress in the degree of semiconductor integration. The above physical cleaning methods have the drawback of serious physical damage done to such patterns.
Conversely, the chemical cleaning methods, particularly the xe2x80x9cmist jet scrub methodxe2x80x9d, is capable of increasing the rate of delivery of the cleaning liquid in mist near the velocity of sound. Sufficient cleaning effect is achieved by using only super pure water as cleaning liquid, without using acid or alkali as cleaning liquid. Of course, acid or alkali may be used as cleaning liquid. Since no direct contact is made with substrates, patterns are free from physical damage.
However, the conventional xe2x80x9cmist jet scrub methodxe2x80x9d noted above also has the following drawback.
Though, as a main task, particles adhering to a substrate surface before cleaning are removed, particles newly generated in the course of cleaning are not removed but remain adhering to the substrate surface after the cleaning. A large part of the particles newly generated is particles from the cleaning nozzle. However, little or no consideration has been made as to a method of suppressing such particles generated from the cleaning nozzle.
This invention has been made having regard to the state of the art noted above, and its object is to provide a cleaning nozzle and a substrate cleaning apparatus capable of suppressing particles generated from the cleaning nozzle.
To fulfill the above object, the following findings have been made.
As noted above, little or no consideration has been made as to a method of suppressing particles generated from the cleaning nozzle.
Inventors carried out experiment with regard to various locations in the cleaning nozzle, on the assumption that particle generation from the cleaning nozzle was caused by abrasion of inner wall surfaces of the cleaning nozzle.
Referring to FIG. 1, inner wall surfaces f of a cleaning nozzle 1 are rough surfaces. As a result, the inner wall surfaces f are found to undergo abrasion by a gas G since the gas G in the cleaning nozzle 1 has been pressurized and compressed. The cleaning nozzle 1 has a mixing portion 3 where the gas G is mixed with a cleaning liquid S to form mist M. In the mixing portion 3 in particular, abrasion of the inner walls of the cleaning nozzle is found most conspicuous. This is due to surface irregularities caused by flaws or the like made in time of manufacturing the cleaning nozzle. Such irregularities are abraded to generate dust particles.
Then, Inventors considered that a large part of the particles generated from the cleaning nozzle resulted from abrasion of the inner wall surfaces of the mixing portion of the cleaning nozzle. A cleaning nozzle has been invented, which has inner wall surfaces of the mixing portion of the cleaning nozzle less susceptible to abrasion, thereby to suppress particle generation from the cleaning nozzle.
The present invention made on the above findings provides the following construction.
A cleaning nozzle according to the present invention has a mixing portion for mixing a cleaning liquid and a pressurized gas to form mist, and discharges the mist formed in the mixing portion, wherein the cleaning nozzle has inner walls of at least the mixing portion presenting smooth surfaces.
The cleaning nozzle according to the invention has at least inner walls of the mixing portion presenting smooth surfaces. This construction is effective to suppress abrasion of the inner wall surfaces of the mixing portion of the cleaning nozzle, thereby suppressing particle generation from the cleaning nozzle.
A preferred example of the material for forming the inner wall surfaces of the mixing portion is quartz. Quartz is a hard material which is effective for preventing abrasion of the inner wall surfaces of the cleaning nozzle in order to suppress particle generation from the cleaning nozzle. Of course, other materials may be used, such as ceramics and sapphire, as long as the inner wall surfaces of the mixing portion are formed smooth.
It is sufficient to have at least the inner wall surfaces of the mixing portion formed smooth. Thus, the entire inner walls of the cleaning nozzle, or the main body of the cleaning nozzle, may be formed of a material, such as quartz, that presents smooth surfaces.
Preferably, the inner walls have a degree of smoothness with surface irregularities in a range of 0.3 xcexcm and less, and more preferably in a range of 0.1 xcexcm and less. The above ranges allow for an increase effect of suppressing abrasion of the inner wall surfaces of the mixing portion of the cleaning nozzle. As a result, particle generation from the cleaning nozzle may be suppressed still further.
The construction of the cleaning nozzle is not limited to that shown in FIG. 1, for example, where a gas introduction pipe for introducing the gas surrounds a supply pipe for supplying the cleaning liquid. It is preferred that the supply pipe surrounds the gas introduction pipe. Where the supply pipe surrounds the gas introduction pipe, the mixing portion has reduced areas for direct contact between the gas and the inner wall surfaces of the cleaning nozzle. The reduced contact areas further suppress abrasion of the inner wall surfaces of the cleaning nozzle, thereby further suppressing particle generation from the cleaning nozzle.
The cleaning nozzle is not limited to a particular shape. It is preferred, however, that the gas introduction pipe is shaped cylindrical or the cleaning nozzle has a main body thereof shaped cylindrical, or the gas introduction pipe extends linearly to the mixing portion. This provides reduced areas for the gas and mist to collide with the inner walls of the gas introduction pipe and cleaning nozzle to suppress particle generation.
The material for presenting smooth surfaces, such as quartz, preferably has the surfaces smoothed by surface treatment.
A substrate cleaning apparatus according to the present invention for cleaning a substrate by supplying a cleaning liquid turned into mist to the substrate, comprises a cleaning nozzle having a mixing portion for mixing the cleaning liquid and a pressurized gas to form mist, and discharging the mist formed in the mixing portion, wherein the cleaning nozzle has at least inner walls of the mixing portion presenting smooth surfaces.
In the substrate cleaning apparatus according to the present invention, the cleaning nozzle according to the invention suppresses particle generation therefrom, thereby preventing particles from being newly generated in time of cleaning. As a result, particles adhering to the substrate surface after the cleaning may also be reduced.
In the substrate cleaning apparatus according to the invention, as in the cleaning nozzle according to the invention, a preferred example of the material for forming the inner wall surfaces of the mixing portion is quartz.